U.S. patent application number 12/945947 was filed with the patent office on 2012-05-17 for method for determining an estimated driving range for a vehicle.
This patent application is currently assigned to GM GLOBAL TECHNOLOGY OPERATIONS, INC.. Invention is credited to Matthew A. Herrmann, Christopher A. Kinser.
Application Number | 20120123618 12/945947 |
Document ID | / |
Family ID | 45999151 |
Filed Date | 2012-05-17 |
United States Patent
Application |
20120123618 |
Kind Code |
A1 |
Kinser; Christopher A. ; et
al. |
May 17, 2012 |
METHOD FOR DETERMINING AN ESTIMATED DRIVING RANGE FOR A VEHICLE
Abstract
A method for determining an estimated driving range for a
vehicle that uses battery power for vehicle propulsion, where the
estimate is in the form of a range of values as opposed to a single
value. In one embodiment, the method adds a positive offset value
to an initial estimate value to determine an upper limit, and
subtracts a negative offset value from the initial estimate value
to determine a lower limit. The positive and negative offset values
may be determined separately and on a real-time basis so that the
extent of the overall estimated driving range may be influenced by
the volatility in power consumption and/or power creation.
Inventors: |
Kinser; Christopher A.;
(Grand Blanc, MI) ; Herrmann; Matthew A.; (Royal
Oak, MI) |
Assignee: |
GM GLOBAL TECHNOLOGY OPERATIONS,
INC.
Detroit
MI
|
Family ID: |
45999151 |
Appl. No.: |
12/945947 |
Filed: |
November 15, 2010 |
Current U.S.
Class: |
701/22 |
Current CPC
Class: |
Y02T 10/7044 20130101;
Y02T 10/7241 20130101; B60L 2240/545 20130101; B60L 2260/52
20130101; Y02T 10/705 20130101; G07C 5/08 20130101; B60L 2240/549
20130101; B60L 58/16 20190201; B60L 2210/30 20130101; B60L 2240/547
20130101; Y02T 10/7072 20130101; Y02T 10/72 20130101; B60L 50/66
20190201; B60L 2220/16 20130101; B60L 2250/16 20130101; B60L
2220/12 20130101; Y02T 10/70 20130101; B60L 2210/40 20130101; Y02T
10/7077 20130101; Y02T 10/7005 20130101; B60L 58/12 20190201; B60L
50/16 20190201 |
Class at
Publication: |
701/22 |
International
Class: |
G06F 17/00 20060101
G06F017/00 |
Claims
1. A method for determining an estimated driving range for a
vehicle, comprising the steps of: (a) determining an available
energy for a battery that may be used for vehicle propulsion; (b)
using the available energy from step (a) to determine an
instantaneous rate of change for the battery; (c) using the
instantaneous rate of change from step (b) to determine an average
rate of change for the battery; and (d) using the instantaneous
rate of change from step (b) and the average rate of change from
step (c) to determine the estimated driving range for the vehicle,
wherein the estimated driving range includes a range of values that
is influenced by the volatility in power consumption and/or power
creation regarding the battery.
2. The method of claim 1, wherein step (b) further comprises taking
a derivative of the available energy from step (a) as a function of
time (d/dt) to determine the instantaneous rate of change for the
battery.
3. The method of claim 1, wherein step (c) further comprises
filtering the instantaneous rate of change from step (b) with a
low-pass filter to produce the average rate of change for the
battery.
4. The method of claim 1, wherein step (d) further comprises
comparing the instantaneous rate of change from step (b) to the
average rate of change from step (c) to determine an error, and the
error refers to the difference between the instantaneous and
average rates of change.
5. The method of claim 4, wherein step (d) further comprises
evaluating the error to determine at least one of a negative error
or a positive error, the negative error includes those error values
where the instantaneous rate of change is less than the average
rate of change, and the positive error includes those error values
where the instantaneous rate of change is greater than the average
rate of change.
6. The method of claim 5, wherein step (d) further comprises using
at least one of the negative error or the positive error to
determine at least one of a negative volatility or a positive
volatility, the negative volatility refers to the volatility in
power consumption, and the positive volatility refers to the
volatility in power creation.
7. The method of claim 6, wherein step (d) further comprises
converting at least one of the negative volatility or the positive
volatility into at least one of a negative offset or a positive
offset, and the negative and positive offsets are in units of
distance.
8. The method of claim 7, wherein step (d) further comprises at
least one of subtracting the negative offset from an initial range
estimate to determine a lower range limit, or adding the positive
offset to an initial range estimate to determine an upper range
limit.
9. The method of claim 1, wherein step (d) further comprises
determining an estimated driving range for the vehicle that
includes a lower range limit and an upper range limit, and the
lower and upper range limits are influenced by the volatility in
power consumption and/or power creation regarding the battery.
10. The method of claim 9, wherein the lower range limit and the
upper range limit are determined separately so that they are
asynchronous.
11. The method of claim 1, further comprising the step of: clipping
the lower range limit if the estimated driving range becomes too
low so that the lower range limit does not include negative
values.
12. The method of claim 1, further comprising at least one of the
following steps: reducing the negative offset so that the estimated
driving range is tightened if there is a decrease in power
consumption volatility; increasing the negative offset so that the
estimated driving range is broadened if there is an increase in
power consumption volatility; reducing the positive offset so that
the estimated driving range is tightened if there is a decrease in
power creation volatility; or increasing the positive offset so
that the estimated driving range is broadened if there is an
increase in power creation volatility.
13. A method for determining an estimated driving range for a
vehicle, comprising the steps of: (a) determining an initial range
estimate for a battery that may be used for vehicle propulsion; (b)
determining a negative offset and subtracting the negative offset
from the initial range estimate to determine a lower range limit;
(c) determining a positive offset and adding the positive offset to
the initial range estimate to determine an upper range limit; and
(d) providing an estimated driving range to a user interface in the
vehicle, wherein the estimated driving range includes the lower
range limit and the upper range limit.
14. The method of claim 13, further comprising the steps of: (i)
determining an available energy for the battery; (ii) using the
available energy to determine an instantaneous rate of change for
the battery; (iii) using the instantaneous rate of change to
determine an average rate of change for the battery; and (iv) using
the instantaneous rate of change and the average rate of change to
determine the negative offset and the positive offset.
15. The method of claim 14, wherein step (iv) further comprises
comparing the instantaneous rate of change from step (ii) to the
average rate of change from step (iii) to determine an error, and
the error refers to the difference between the instantaneous and
average rates of change.
16. The method of claim 15, wherein step (iv) further comprises
evaluating the error to determine at least one of a negative error
or a positive error, the negative error includes those error values
where the instantaneous rate of change is less than the average
rate of change, and the positive error includes those error values
where the instantaneous rate of change is greater than the average
rate of change.
17. The method of claim 16, wherein step (iv) further comprises
using at least one of the negative error or the positive error to
determine at least one of a negative volatility or a positive
volatility, the negative volatility refers to the volatility in
power consumption, and the positive volatility refers to the
volatility in power creation.
18. The method of claim 17, wherein step (iv) further comprises
converting at least one of the negative volatility or the positive
volatility into at least one of the negative offset or the positive
offset, and the negative and positive offsets are in units of
distance.
19. The method of claim 13, wherein the lower range limit and the
upper range limit are determined separately so that they are
asynchronous.
20. The method of claim 13, further comprising the step of:
clipping the lower range limit if the estimated driving range
becomes too low so that the lower range limit does not include
negative values.
21. The method of claim 13, further comprising at least one of the
following steps: reducing the negative offset so that the estimated
driving range is tightened if there is a decrease in power
consumption volatility; increasing the negative offset so that the
estimated driving range is broadened if there is an increase in
power consumption volatility; reducing the positive offset so that
the estimated driving range is tightened if there is a decrease in
power creation volatility; or increasing the positive offset so
that the estimated driving range is broadened if there is an
increase in power creation volatility.
Description
TECHNICAL FIELD
[0001] The present invention generally relates to vehicles and,
more particularly, to methods for determining estimated driving
ranges for vehicles that use battery power for vehicle
propulsion.
BACKGROUND
[0002] Some vehicles provide an estimated driving range in the form
of a single value (e.g., miles until empty). This single value is
displayed on the vehicle's instrument panel, and can be beneficial
by providing the driver with an estimate as to how far the vehicle
can be driven before running out of fuel. However, such an estimate
is only accurate so long as the vehicle continues to be driven in a
similar or constant manner. For example, if the driver transitions
from highway to city driving, then the estimated driving range
could change significantly.
SUMMARY
[0003] According to one embodiment, there is provided a method for
determining an estimated driving range for a vehicle. The method
may comprise the steps of: (a) determining an available energy for
a battery that may be used for vehicle propulsion; (b) using the
available energy to determine an instantaneous rate of change for
the battery; (c) using the instantaneous rate of change to
determine an average rate of change for the battery; and (d) using
the instantaneous rate of change and the average rate of change to
determine the estimated driving range for the vehicle, wherein the
estimated driving range may include a range of values that is
influenced by the volatility in power consumption and/or power
creation regarding the battery.
[0004] According to another embodiment, there is provided a method
for determining an estimated driving range for a vehicle. The
method may comprise the steps of: (a) determining an initial range
estimate for a battery that may be used for vehicle propulsion; (b)
determining a negative offset and subtracting the negative offset
from the initial range estimate to determine a lower range limit;
(c) determining a positive offset and adding the positive offset to
the initial range estimate to determine an upper range limit; and
(d) providing an estimated driving range to a user interface in the
vehicle, wherein the estimated driving range includes the lower
range limit and the upper range limit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] Preferred exemplary embodiments will hereinafter be
described in conjunction with the appended drawings, wherein like
designations denote like elements, and wherein:
[0006] FIG. 1 is a perspective view depicting an exemplary
vehicle;
[0007] FIG. 2 is a block diagram illustrating some of the steps of
an exemplary method that may be used to determine an estimated
driving range for a vehicle, such as the one shown in FIG. 1;
[0008] FIG. 3 shows several exemplary plots that help illustrate
some of the techniques that may be used by the method of FIG. 2;
and
[0009] FIG. 4 shows an exemplary presentation of an estimated
driving range that may be presented via a user interface.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0010] The method described below may determine an estimated
driving range for a vehicle that uses battery power for vehicle
propulsion, where the estimate is in the form of a range of values
as opposed to a single value. As previously mentioned, the
estimated driving range can be significantly impacted by the manner
in which the vehicle is driven. By providing an estimated driving
range in the form of a range of values that are bound by upper and
lower limits, the present method may provide the driver with more
useful estimates. In one embodiment, the method adds a positive
offset value to an initial estimate value to determine an upper
limit, and subtracts a negative offset value from the initial
estimate value to determine a lower limit. The positive and
negative offset values may be determined separately so that the
extent of the overall range is influenced by the volatility in
power consumption and/or power creation. In periods of low
volatility (i.e., rather consistent and steady power consumption or
creation), the overall estimated driving range is rather tight (the
method is more confident of the estimate and therefore provides a
narrower range). In periods of high volatility, the overall
estimated driving range is rather broad, as the method is less
confident in its estimate and thus needs a broader range to account
for this. The following explanation of exemplary method 100 is
provided in conjunction with the block diagram shown in FIG. 2, the
graphs shown in FIG. 3, and the estimated driving range
presentation shown in FIG. 4.
[0011] With reference to FIG. 1, there is shown portions of an
exemplary vehicle 10, for which an estimated driving range may be
determined It should be appreciated that FIG. 1 is only a schematic
representation of certain portions of a vehicle and that the method
described herein could be used with any number of different
vehicles and systems and is not limited to the exemplary one shown
here. For example, the method described below can be used with a
hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle
(PHEV), an extended-range electric vehicle (EREV), a battery
electric vehicle (BEV), or any other vehicle that uses battery
power for vehicle propulsion. According to this particular
embodiment, vehicle 10 generally includes a battery 30, an electric
motor 32, a control module 34, and a user interface 36.
[0012] Battery 30 may store electrical energy that is used to drive
electric motor 32, as well as to meet other electrical needs of the
vehicle. According to an exemplary embodiment, battery 30 includes
a high-voltage battery pack 50 (e.g., 40V-600V), a sensor unit 52,
and a control unit 54. Battery pack 50 may include a number of
individual battery cells and may utilize any suitable battery
chemistry, including those that are based on the following
technologies: lithium ion, nickel metal hydride (NiMH), nickel
cadmium (NiCd), sodium nickel chloride (NaNiCl), or some other
battery technology. Battery 30 should be designed to withstand
repeated charge and discharge cycles and may be used in conjunction
with other energy storage devices, such as capacitors, super
capacitors, inductors, etc. Those skilled in the art will
appreciate that battery 30 may be provided according to any number
of different embodiments, may be connected in any number of
different configurations, and may include any number of different
components, like sensors, control units and/or any other suitable
components known in the art.
[0013] Battery sensor unit 52 may include any variety of different
sensing components or elements, and may monitor battery conditions
such as battery voltage, current, state of charge (SOC), state of
health (SOH), temperature, etc. These sensors may be integrated
within battery unit 30 (e.g., an intelligent or smart battery),
they may be external sensors located outside of the battery unit,
or they may be provided according to some other known arrangement.
The battery sensors may monitor and determine the battery voltage,
current, SOC, SOH, temperature, etc. on a cell-by-cell basis, as an
average of a collection or block of cells or region of the battery
unit, as an average of the entire battery unit, or according to
some other method known in the art. Output from battery sensor unit
50 may be provided to control unit 54, control module 34, or some
other appropriate device.
[0014] Battery Control unit 54 may include any variety of
electronic processing devices, memory devices, input/output (I/O)
devices, and other known components, and may perform various
control and/or communication related functions. For example,
control unit 54 could receive sensor signals from battery sensor
unit 52, package the sensor signals into an appropriate sensor
message, and send the sensor message to control module 34 over an
appropriate connection, such as a CAN bus, a system management bus
(SMBus), a proprietary communication link, or any other
communication means known to those skilled in the art. It is
possible for control unit 54 to gather battery sensor readings and
store them in local memory so that a comprehensive sensor message
can be provided to control module 34 at a later time, or the sensor
readings can be forwarded to module 34 or some other destination as
soon as they arrive at control unit 54, to cite a few
possibilities. In another capacity, battery control unit 54 can
store pertinent battery characteristics and background information
pertaining to the battery's cell chemistry, cell capacity, upper
and lower battery voltage limits, battery current limits, battery
temperature limits, temperature profiles, battery impedance, number
or history of charge/discharge events, etc.
[0015] Electric motor 32 may use electrical energy stored in
battery 30 to drive one or more vehicle wheels, which in turn
propels the vehicle. While FIG. 1 schematically depicts electric
motor 32 as a single discrete device, the electric motor may be
combined with a generator (a so-called "mogen") or it may include
multiple electric motors (e.g., separate motors for the front and
rear wheels, separate motors for each wheel, separate motors for
different functions, etc.), to cite a few possibilities. System 10
is not limited to any one particular type of electric motor, as
many different motor types, sizes, technologies, etc. may be used.
In one example, electric motor 32 includes an AC motor (e.g., a
three-phase AC induction motor, a multi-phase AC induction motor,
etc.) as well as a generator that can be used during regenerative
braking. Electric motor 32 may be provided according to any number
of different embodiments (e.g., AC or DC motors, brushed or
brushless motors, permanent magnet motors, etc.), may be connected
in any number of different configurations, and may include any
number of different components, like cooling features, sensors,
control units and/or any other suitable components known in the
art.
[0016] Control module 34 may be used to control, govern or
otherwise manage certain operations or functions of vehicle 10 and,
according to one exemplary embodiment, includes a processing device
70 and a memory device 72. Processing device 70 may include any
type of suitable electronic processor (e.g., a microprocessor, a
microcontroller, an application specific integrated circuit (ASIC),
etc.) that executes instructions for software, firmware, programs,
algorithms, scripts, etc. This processor is not limited to any one
type of component or device. Memory device 72 may include any type
of suitable electronic memory means and may store a variety of data
and information. This includes, for example: sensed vehicle
conditions; look-up tables and other data structures; software,
firmware, programs, algorithms, scripts, and other electronic
instructions; component characteristics and background information,
etc. The present method--as well as any other electronic
instructions and/or information needed for such tasks--may also be
stored or otherwise maintained in memory device 72. Control module
34 may be electronically connected to other vehicle devices and
modules via I/O devices and suitable connections, like a
communications bus, so that they can interact as required. These
are, of course, only some of the possible arrangements, functions
and capabilities of control module 34, as others are certainly
possible. Depending on the particular embodiment, control module 34
may be a stand-alone electronic module (e.g., a vehicle integration
control module (VICM), a traction power inverter module (TPIM), a
battery power inverter module (BPIM), etc.), it may be incorporated
or included within another electronic module in the vehicle (e.g.,
a power train control module, an engine control module, etc.), or
it may be part of a larger network or system (e.g., a battery
management system (BMS), a vehicle energy management system, etc.),
to name a few possibilities.
[0017] User interface 36 may include any variety of different
software and/or hardware components to exchange information between
the vehicle and a user. This includes, for example, output
components like a visual display, an instrument panel, or an audio
system where user interface 36 provides information to a vehicle
user. This also includes input components like a touch-screen
display, a microphone, a keyboard, a pushbutton or other control
where user interface 36 receives information from a vehicle user.
In some cases, user interface 36 includes components with both
input and output capabilities, such as a visual interface and an
audible interface. A visual interface may include any suitable
interface that is located within the vehicle and visually presents
information to and/or receives information from a vehicle user, and
it may be driven by a sequence of navigable menus that enable the
user to exchange information with the vehicle. A visual
touch-screen display is one example of a suitable visual interface.
Likewise, an audible interface may include any suitable interface
that is located within the vehicle and audibly presents information
to and/or receives information from a user, and it may be part of
an on-board automated voice processing system that uses
voice-recognition and/or other human-machine interface (HMI)
technology. User interface 36 may be a stand-alone module; it may
be part of an infotainment system or part of some other module,
device or system in the vehicle; it may be mounted on a dashboard
(e.g., with a driver information center (DIC)); it may be projected
onto a windshield (e.g., with a heads-up display); it may be
integrated within an existing audio system; or it may simply
include an electronic connection or port for connecting with a
laptop or other computing device, to cite a few examples.
[0018] As explained below in more detail, user interface 36 may be
used by the present method to provide information in a graphical
form from the vehicle to a vehicle user. For instance, user
interface 36 may provide an estimated driving range, charging
status, instant consumption, average consumption, reports and/or
other output to a vehicle user. Other user interfaces may be used
instead, as the exemplary user interface shown and described herein
represents only one possibility. The present method may utilize any
user interface to provide information from the vehicle to a vehicle
user, and is not limited to any particular type.
[0019] Turning now to FIG. 2, there is shown an exemplary method
100 for determining an estimated driving range for a vehicle that
uses battery power for vehicle propulsion, where the estimate is in
the form of a range of values as opposed to a single value. As
previously mentioned, the estimated driving range can be
significantly impacted by the manner in which the vehicle is driven
(e.g., aggressive versus passive driving, highway versus city
driving, etc.). By providing an estimated driving range in the form
of a range of values that are bound by upper and lower limits, the
present method may provide the driver with more useful estimates.
In one embodiment, method 100 adds a positive offset value to an
initial estimate value to determine an upper limit, and subtracts a
negative offset value from the initial estimate value to determine
a lower limit. The upper and lower limits define the estimated
driving range, which may be provided to the vehicle user in the
form of a visual presentation via user interface 36. The following
explanation of exemplary method 100 is provided in conjunction with
the block diagram shown in FIG. 2 and the graphs shown in FIG.
3.
[0020] Beginning with step 110, the method starts by determining
the available energy in battery 30. The available or remaining
energy may be determined in one of a variety of different ways. In
one embodiment, battery sensor unit 52 measures or otherwise senses
the battery voltage, current, state of charge (SOC), state of
health (SOH) and/or temperature, and provides this information to
control module 34. Control module 34, in turn, uses this
information to determine the `available energy` which corresponds
to the amount of energy available or left in battery 30. In another
embodiment, control module 34 determines the available energy in
battery 30 by obtaining an available energy reading from some other
component, device, module and/or system (e.g., a vehicle
integration control module (VICM)) that is in possession of such
information. It is not necessary that control module 34 determine
the available energy, as this calculation could be performed by
some other device, such as battery control unit 54. Step 110 may
express the available energy in any suitable form, such as in
kilowatt hours (Kw*Hrs). With reference to FIG. 3, there is shown
an exemplary plot 200 which represents the available energy in
battery 30 (y-axis) as a function of time (x-axis). This plot is
only provided for purposes of illustration and is in no way meant
to limit the scope or application of exemplary method 100.
[0021] Next, step 114 determines an instantaneous rate of change
for the available energy in battery 30. Like many of the steps in
method 100, step 114 may be performed in any number of different
ways. For instance, it is possible for step 114 to determine an
`instantaneous rate of change` by taking the derivative of the
available energy, as a function of time (d/dt). The instantaneous
rate of change generally corresponds to the rate of energy usage in
battery 30, and is illustrated in FIG. 3 with exemplary plot 210.
Stated differently, plot 210 represents the rate of change or the
slope of plot 200. Declining segments of plot 200 represent battery
discharge events (e.g., vehicle propulsion) and are represented in
plot 210 with negative values; inclining segments of plot 200
represent battery charge events (e.g., regenerative braking) and
are represented in plot 210 with positive values; and flat segments
of plot 200 represent battery neutral events (e.g, coasting along)
and are represented in plot 210 with values of zero. One can see
from both plots 200 and 210 that battery 30 is discharging during
most of this exemplary time period. Segments where battery 30 is
being rapidly discharged or charged are represented in plot 210 in
the form of peaks and valleys, as these correspond to periods of
increased battery charge volatility. Step 114 may express the
instantaneous rate of change in any suitable form, such as in
kilowatts (Kw). Also, step 114 may perform some degree of basic
signal processing, including light filtering, as the output of this
step is intended to be a "generally" unfiltered or instantaneous
rate of change.
[0022] Step 118 filters, smoothes, or otherwise manipulates the
instantaneous rate of change data that was determined in the
previous step, and may do so according to a number of different
techniques. For example, step 118 may apply some type of filtering
or smoothing function to plot 210, in order to arrive at an
`average rate of change`, such as that illustrated by plot 220. One
can see from these exemplary plots that many of the peaks and
valleys of plot 210 have been smoothed over by the more gradual
segments of plot 220. Skilled artisans will appreciate that various
filtering, smoothing or other signal processing techniques may be
employed by step 118 including, but certainly not limited to,
low-pass, high-pass and band-pass filters, 1.sup.st-, 2.sup.nd- and
3.sup.rd-order filters, Butterworth, Kalman and Savitzky-Golay
filters, local regression techniques, moving averages, Kernel and
Laplacian smoothers, etc. In one embodiment, step 118 employs a
low-pass, 1.sup.st-order filter with a low cutoff frequency (e.g.,
0.25 Hz) to produce the average rate of change illustrated by plot
220. However, other filters and filtering techniques can be used
instead. Step 118 may express the average rate of change in any
suitable form, such as in kilowatts (Kw).
[0023] Next, step 120 compares the instantaneous rate of change
(plot 210) to the average rate of change (plot 220) and determines
an `error` (plot 230), which can have negative and/or positive
values. The error (plot 230) generally refers to the difference or
delta between the instantaneous and average rates of change, which
is illustrated in FIG. 3 with arrows 290. The `negative error`
generally refers to those error values that are less than zero;
that is, points along plot 210 where the y-axis value is less than
that of a corresponding point along plot 220, where both points
have the same x-axis value. To illustrate, consider points 250,
252, which both have the same x-axis value. Point 250 is part of
plot 210 (instantaneous rate of change), and point 252 is part of
plot 220 (average rate of change). Because point 250 has a smaller
y-axis value than point 252 (i.e., is located below point 252 on
the graph), then this value or point is part of the negative error.
The opposite is true for points 260, 262, which correspond to a
`positive error` because point 260 along plot 210 has a larger
y-axis value than point 262 on plot 220. Points along plots 210 and
220 that have the same y-axis value result in a delta or error
value of zero. Step 120 may express the error in any suitable form,
such as in kilowatts (Kw).
[0024] Once the error has been determined, step 122 extracts,
identifies or otherwise determines the `negative error`. As
mentioned above, the negative error generally refers to those error
values that are less than zero. If step 122 encounters values or
points along plot 230 that correspond to a positive error (i.e.,
are greater than zero), then those portions of plot 230 can be
truncated or cut off at the zero mark (see segments 280, 282). For
example, segments 270, 272 and 274 correspond to a negative error,
while segments 280 and 282 correspond to a positive error. This
evaluation of error plot 230 may be performed for the entire plot
or it may be performed on just a segment of the plot. In the
exemplary embodiment illustrated in FIG. 2, the negative and
positive errors are determined separately; however, in another
embodiment, they may be determined at the same time. Step 122 may
express the negative error in any suitable form, such as in
kilowatts (Kw).
[0025] In step 126, the negative error (plot 230) is evaluated with
the instantaneous rate of change (plot 210) in order to determine a
`negative volatility`. A variety of different techniques may be
used to perform this step. In one embodiment, step 126 examines
plots 210 and 230 in order to determine how much and how often the
instantaneous rate of change differs from the average rate of
change, or at least the negative portions thereof This step may use
calculations that behave as a decaying sum--as the negative
portions increase, so does the total sum or area under the curve.
Without further stimulation from `negative volatility`, the sum may
decrease with time. In a sense, step 126 may be used to gauge the
volatility or the amount of fluctuation in power consumption. If
battery 30 were discharged in a slow and steady manner, then the
one would expect the instantaneous rate of change (plot 210) to be
fairly consistent with the negative portions of the error (plot
230), and therefore produce a rather small negative volatility;
this corresponds to a relatively low power consumption volatility.
Conversely, if battery 30 experienced periods of sudden and rapid
charge depletion, then this would likely lead to a rather large
negative volatility; this corresponds to a relatively high power
consumption volatility. This volatility factor may subsequently
impact the estimated driving range of the vehicle, as will be
explained. Step 126 may express the negative volatility in any
suitable form, such as in kilowatt hours (Kw*Hrs).
[0026] Step 130 scales or otherwise converts the negative
volatility from the previous step into a `negative offset`.
According to the exemplary embodiment described above, step 126
produces a negative volatility value or factor that is in units of
energy, like kilowatt hours (Kw*Hrs), but the estimated driving
range that method 100 ultimately seeks to determine is in units of
distance, such as kilometers (Km). Thus, a conversion needs to take
place to convert from energy to distance and, hence, negative
volatility to negative offset. Step 130 may perform this conversion
according to a number of different techniques, including using a
calibration approach that uses stored empirical data. For example,
a lookup table 150 or other data structure may be maintained in
memory device 72 or some other appropriate location on the vehicle,
where the data structure stores scaling calibration data that is
empirically determined by driving the car around and evaluating the
relationship between energy and distance. In a different
embodiment, scaling data is based on predetermined or known
relationships between different units, as opposed to being
empirically determined. Of course, other techniques for scaling or
converting units may also be used, as the preceding example is only
one possibility. Thus, step 130 may express the negative offset in
any suitable form, such as in kilometers (Km) or miles.
[0027] An optional filtering step 134 may be used to smooth or
otherwise filter the negative offset. This may prevent abrupt and
instantaneous changes in the negative offset value. According to an
exemplary embodiment, optional step 134 uses a first-order filter
to filter or process the negative offset determined in the previous
step. Other filters and filtering techniques may be used
instead.
[0028] Next, step 138 subtracts the negative offset from an
`initial range estimate` 302 in order to arrive at a `lower range
limit`. Skilled artisans will appreciate that numerous techniques
may be used to provide an initial range estimate, which is a
single-value estimate for the range or distance left before the
vehicle needs to be recharged, refueled, etc. Method 100 is not
limited to any particular method or technique for determining an
initial range estimate, which may be provided by control module 34
or some other source. According to an exemplary embodiment, step
138 uses both a short term filter (e.g., 8 mile range) and a long
term filter (e.g., 80 mile range) to generate the initial range
estimate, however, other techniques may be used instead. For
example, step 138 may use a Federal Transportation Procedure (FTP)
range (e.g., average energy per mile), a moving average, a battery
energy estimate, or some other suitable range prediction method.
Consider the example illustrated in FIG. 4, where the negative
offset value 300 from the previous step is 6.0 miles and the
initial range estimate 302 from control module 34 is 19.0 miles;
step 138 subtracts the 6.0 miles from the 19.0 miles to arrive at a
lower range limit 304 of 13.0 miles.
[0029] A similar process may be used to determine a `positive
offset`, which is added to the same initial range estimate to
arrive at an `upper range limit`. For example, step 222 may receive
error information from step 120 and produce a `positive error`, in
much the same way as step 122 produces a negative error and as
described above in greater detail. Step 226 may then receive the
positive error from step 222 and the instantaneous rate of change
from step 114, and use this information to generate a `positive
volatility`, as was similarly done in step 126. In a sense, the
positive volatility is representative of the volatility or variance
in power creation. The positive volatility value may then be
converted in step 230 into a `positive offset` using a lookup table
250, which may be optionally filtered at step 234 before being
provided to step 238. Step 238 may add the positive offset to the
initial range estimate in order to arrive at an upper range limit.
Because of the similarity between steps 122, 222; 126, 226; 130,
230; 134, 234; and 138, 238, respectively, separate descriptions of
the corresponding steps used to determine the upper range limit
have been omitted. The descriptions provided above in conjunction
with the lower range limit apply to steps 222, 226, 230, 234 and
238 as well.
[0030] Continuing with the example from above, assume that the
positive offset value 310 is 4.0 miles. Step 238 adds 4.0 miles to
19.0 miles to arrive at an upper range limit 312 of 23.0 miles.
This results in an overall estimated driving range 320 of 13.0 to
23.0 miles, where the extent or expanse of the overall range is
influenced by the volatility in power consumption and power
creation. In periods of low volatility (i.e., rather consistent and
steady power consumption or creation), the overall estimated
driving range 320 may be rather tight (the method is more confident
of the estimate and therefore provides a tighter or narrower
range). In periods of high volatility, the overall estimated
driving range 320 may be rather broad, as the method is less
confident in its estimate or prediction and thus needs a broader
range to account for this.
[0031] If the estimated driving range becomes quite low because
battery 30 is almost out of charge, a clipping function or the like
may be used to clip, truncate or otherwise modify the lower range
limit 304. For instance, if the initial range estimate 302 is at
3.0 miles and the negative offset 300 is 4.0 miles, in the absence
of a clipping function this would result in a lower range limit 304
of -1.0 mile. The clipping function may simply limit the lower
range limit to 0.0 miles so that "negative distances" are not
provided to the user, or it may employ some other technique.
[0032] It should be noted that negative and positive offsets may be
the same (symmetrical) or they may differ (asymmetrical). This is
because the negative and positive offsets are separately influenced
by the negative and positive volatilities, respectively. If battery
30 is discharging at a more volatile rate than it is charging, then
the negative offset will likely be larger than the positive offset.
In another embodiment, the present method may use some of the steps
described above to arrive at a single offset value that is then
added and subtracted from a primary range prediction; this is an
example of symmetrical offsets, where the negative and positive
offsets are determined together, instead of separately. The output
that is generated by exemplary method 100 and is presented to the
user (e.g., that shown in FIG. 4) not only includes information
about the estimated driving range, but it also includes information
about the confidence of the prediction. The smaller the offset
values and the tighter the overall estimated driving range 320, the
more confident the exemplary algorithm is about the estimate; the
larger the offset values and the wider the overall estimated
driving range, the less confident the exemplary algorithm is about
the estimate. Accordingly, the present method may use real-time
statistical analysis of the vehicle's power consumption and/or
power creation to calculate or otherwise determine the estimated
driving range, which includes both range information and confidence
information.
[0033] It is to be understood that the foregoing description is not
a definition of the invention, but is a description of one or more
preferred exemplary embodiments of the invention. The invention is
not limited to the particular embodiment(s) disclosed herein, but
rather is defined solely by the claims below. Furthermore, the
statements contained in the foregoing description relate to
particular embodiments and are not to be construed as limitations
on the scope of the invention or on the definition of terms used in
the claims, except where a term or phrase is expressly defined
above. Various other embodiments and various changes and
modifications to the disclosed embodiment(s) will become apparent
to those skilled in the art. For example, the specific combination
and order of steps is just one possibility, as the present method
may include a combination of steps that has fewer, greater or
different steps than that shown here. It is not necessary that the
negative offset be determined before the positive offset, as the
positive offset may be determined first or they may be determined
at the same time, for example. All such other embodiments, changes,
and modifications are intended to come within the scope of the
appended claims.
[0034] As used in this specification and claims, the terms "for
example," "e.g.," "for instance," "such as," and "like," and the
verbs "comprising," "having," "including," and their other verb
forms, when used in conjunction with a listing of one or more
components or other items, are each to be construed as open-ended,
meaning that that the listing is not to be considered as excluding
other, additional components or items. Other terms are to be
construed using their broadest reasonable meaning unless they are
used in a context that requires a different interpretation.
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